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Subject[PATCH] xacct_add_tsk: fix pure theoretical ->mm use-after-free
Paranoid fix. The task can free its ->mm after the 'if (p->mm)' check.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- STATS/kernel/tsacct.c~3_mm 2006-10-27 01:03:26.000000000 +0400
+++ STATS/kernel/tsacct.c 2006-10-29 21:46:12.000000000 +0300
@@ -80,13 +80,17 @@ void bacct_add_tsk(struct taskstats *sta
*/
void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
{
+ struct mm_struct *mm;
+
/* convert pages-jiffies to Mbyte-usec */
stats->coremem = jiffies_to_usecs(p->acct_rss_mem1) * PAGE_SIZE / MB;
stats->virtmem = jiffies_to_usecs(p->acct_vm_mem1) * PAGE_SIZE / MB;
- if (p->mm) {
+ mm = get_task_mm(p);
+ if (mm) {
/* adjust to KB unit */
- stats->hiwater_rss = p->mm->hiwater_rss * PAGE_SIZE / KB;
- stats->hiwater_vm = p->mm->hiwater_vm * PAGE_SIZE / KB;
+ stats->hiwater_rss = mm->hiwater_rss * PAGE_SIZE / KB;
+ stats->hiwater_vm = mm->hiwater_vm * PAGE_SIZE / KB;
+ mmput(mm);
}
stats->read_char = p->rchar;
stats->write_char = p->wchar;
-
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